In early March, after weeks of debate across a conference table in the Eisenhower Executive Office Building, the participants in President Obama's strategic review of the war in Afghanistan figured that the most contentious part of their discussions was behind them. Everyone, save Vice President Biden's national security adviser, agreed that the United States needed to mount a comprehensive counterinsurgency mission to defeat the Taliban.

That conclusion, which was later endorsed by the president and members of his national security team, would become the first in a set of recommendations contained in an administration white paper outlining what Obama called "a comprehensive, new strategy for Afghanistan and Pakistan." Preventing al-Qaeda's return to Afghanistan, the document stated, would require "executing and resourcing an integrated civilian-military counterinsurgency strategy."

To senior military commanders, the sentence was unambiguous: U.S. and NATO forces would have to change the way they operated in Afghanistan. Instead of focusing on hunting and killing insurgents, the troops would have to concentrate on protecting the good Afghans from the bad ones.

And to carry out such a counterinsurgency effort the way its doctrine prescribes, the military would almost certainly need more boots on the ground.

To some civilians who participated in the strategic review, that conclusion was much less clear. Some took it as inevitable that more troops would be needed, but others thought the thrust of the new approach was to send over scores more diplomats and reconstruction experts. They figured a counterinsurgency mission could be accomplished with the forces already in the country, plus the 17,000 new troops Obama had authorized in February.

"It was easy to say, 'Hey, I support COIN,' because nobody had done the assessment of what it would really take, and nobody had thought through whether we want to do what it takes," said one senior civilian administration official who participated in the review, using the shorthand for counterinsurgency.

The failure to reach a shared understanding of the resources required to execute the strategy has complicated the White House's response to the grim assessment of the war by the top U.S. and NATO commander in Afghanistan, forcing the president to decide, in effect, what his administration really meant when it endorsed a counterinsurgency plan. Gen. Stanley A. McChrystal's follow-up request for more forces, which presents a range of options but makes clear that the best chance of achieving the administration's goals requires an additional 40,000 U.S. troops on top of the 68,000 who are already there, has given senior members of Obama's national security team "a case of sticker shock," the administration official said.

The meetings now underway in Washington are rooted in part in the gap in understanding that became evident in March. This account of how it opened up is based on interviews with several senior civilian members of the administration and military officers directly involved in Afghanistan issues. Nearly all spoke on the condition of anonymity because they were not authorized to talk publicly about internal policy discussions.

As the president's top defense and foreign policy officials debate the way forward, they have begun to revisit the March review's main conclusion, asking whether the administration's relatively narrow goal of preventing al-Qaeda's return to Afghanistan would best be achieved through a full-on counterinsurgency mission or through a more limited counterterrorism operation that would target any high-level terrorists seeking to operate there again.

This time, the discussions about counterinsurgency will not remain theoretical or involve back-of-the-envelope estimates of troop levels. It is clear to all around the table now that pursuing a full counterinsurgency, at least according to the model developed in Iraq by Gen. David H. Petraeus and embraced by McChrystal, would entail tens of thousands of additional troops, legions of civilian specialists and billions more reconstruction dollars.

Senior military leaders, including Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, and Petraeus, who now heads the U.S. Central Command, have indicated their support for McChrystal's request in discussions with administration officials. Biden has taken the opposite view, renewing arguments he made earlier this year for a narrower counterterrorism mission instead of a comprehensive counterinsurgency campaign. Others, including Defense Secretary Robert M. Gates and Secretary of State Hillary Rodham Clinton, have not staked out a firm position.

With the costs now clearer, some officials at the National Security Council and the State Department who voiced support for counterinsurgency in March have started to consider other options. There is increasing interest in Biden's stance, as well as in a modified counterinsurgency effort that would involve sending more military trainers but not more combat forces.

"The skeptics are growing," one senior official said.

Asked why Obama is questioning a key assumption of his Afghanistan strategy just six months after he stood before a bank of flags and endorsed the white paper, administration spokesmen have cited the potential impact on counterinsurgency efforts of the country's fraud-riddled presidential election in August. They have also noted that Obama said in March that he would review whether the United States was "using the right tools and tactics to make progress."

But senior officials involved in Afghanistan strategy discussions now and earlier this year said the lack of agreement in March about counterinsurgency will make these deliberations more protracted and disputatious.

"We're going back to key assumptions," one official said.

Agreement on the Goal

Less than three weeks after Obama took office, the White House selected former CIA officer Bruce Riedel to review U.S. policy toward Afghanistan and Pakistan. Riedel was told to consult broadly but act quickly: The president wanted his conclusions by mid-March, before a NATO summit in Europe early in April.

Working with national security adviser James L. Jones and his top aides, Riedel assembled a team that included representatives from the Defense and State departments and the CIA. A senior official from the Joint Chiefs of Staff was there. So, too, was Biden's national security adviser, Antony Blinken, and Lt. Gen. Douglas E. Lute, who was President George W. Bush's Iraq war czar but was kept on by Jones to help manage Afghanistan war policy for the National Security Council. Petraeus and Richard C. Holbrooke, the administration's point man at the State Department for Afghanistan and Pakistan, often attended the group's meetings.

In a campaign speech in June 2008, Obama called the fight against al-Qaeda in Afghanistan and in the frontier regions of Pakistan "a war that we must win." He did not mention the Taliban, the insurgents battling U.S. forces and the Afghan government. Although the Taliban welcomed Osama bin Laden when it ruled Afghanistan, U.S. intelligence officials say they believe there are few, if any, links between Taliban commanders in Afghanistan today and senior al-Qaeda members.

Obama's choice of words was not lost on members of the review team. They, too, argued that the United States should focus on al-Qaeda. Their final document made the point bluntly: "The core goal of the U.S. must be to disrupt, dismantle, and defeat al-Qaeda."

But the question of how to achieve that end provoked pointed debate. Most participants insisted that the only way to prevent al-Qaeda from returning to Afghanistan would be to build up an Afghan government, with a large enough police force and army to defend itself. That would require continued U.S. assistance, in reconstruction and in fighting the Taliban. And that meant counterinsurgency.

Blinken, speaking for his boss, argued that trying to build an Afghan state strong enough to withstand the Taliban would take more time and resources than the American public would be willing to tolerate. If the goal is defeating al-Qaeda, he said, the United States should pursue a more focused strategy, targeting terrorists who seek to set up operations in Afghanistan.

One participant described the counterinsurgency vs. counterterrorism debate as "very spirited." But, the participant said, referring to Blinken, "at the end of the day, he was a minority of one."

Counterterrorism is "what the Bush administration did largely for seven years, and it didn't work," Riedel said. "And it's not likely to work in the future."

Divergence on the Means

The review team had reached a consensus that more troops were needed to pursue a counterinsurgency strategy. Members made rough estimates based on traditional counterinsurgency doctrine. But the numbers depended on how much of the country required such an approach -- parts of the north and west were deemed sufficiently quiescent -- and how many Afghan security forces could be added to the mix.

"I don't think anyone had any illusions that this was going to be cheap and easy," Riedel said.

In March, however, it was not clear to several of the participants that a significant addition of U.S. forces would be needed. Obama had only recently authorized the deployment of 17,000 more troops. Most would be heading to Helmand and Kandahar provinces in the south, where the insurgents were making gains. Later that month, Obama agreed to send 4,000 more soldiers to help train the Afghan army. Several team members assumed those forces would prove sufficient.

Encouraging the view that a massive influx was not needed were statements from the overall U.S. and NATO commander at the time, Gen. David D. McKiernan, who said he had shifted his troops toward counterinsurgency operations. He was not asking for more forces beyond the 21,000 Obama had agreed to, plus 10,000 more in 2010, which the Pentagon told the White House it could address later in the year.

"Typically, you defer to the field for the resource needs," said one senior official involved in the review. "In March . . . we thought we had a handle on what McKiernan thought he needed."

A military official familiar with McKiernan's thinking said his request for 30,000 troops last fall was tempered by a belief that the Bush White House would reject it outright if he asked for more. As it was, Bush tabled the request, leaving it to Obama.

Another wild card was the role civilians would play in an expanded counterinsurgency mission. The review team agreed with Holbrooke's request to dispatch hundreds more development specialists and to overhaul U.S. reconstruction programs.

"The civilian component is just as important as the troops," the senior official said. "We knew they'd play a crucial role, and they'd help reduce the need for more troops."

All of the top members of Obama's national security team, including Gates, Clinton, Mullen and Jones, endorsed the report. Biden, who also participated in the final rounds of top-level discussions, maintained his objections to the counterinsurgency mission.

In mid-March, Riedel briefed Obama. Among the points he made was that, by the Pentagon's estimate, it costs $250,000 to keep a U.S. soldier in Afghanistan for a year. An Afghan soldier costs about $12,000.

The gist of what Riedel said, according to a person familiar with the conversation, was: "It's far more efficient to train Afghans who can speak the language, drink the water, understand the culture -- that's our ticket out. That's how we come to a good end here. . . . But while we're building up the Afghan security forces, we have to provide the security environment in which that will take place, and that means a significant force to do it."

But what Riedel could not tell the president was whether the 21,000 troops he had authorized -- plus the 10,000 on order, plus the hundreds of civilians -- would be sufficient.

"The military was not ready at that point to come to the president and say, 'Here's the number we think it's going to take,' " the person familiar with the conversation said. "They were satisfied that what they had put on the table at the beginning of the administration met their requirement for the moment."

McChrystal's Thinking

At the same time that the counterinsurgency idea was taking hold among the review team's members, Mullen and Gates were starting to question whether McKiernan was the right general to lead the effort in Afghanistan. If he was serious about counterinsurgency, some in the Pentagon wondered, how could he not want more forces?

To senior military planners, counterinsurgency had a clear meaning -- and a defined prescription. The military's counterinsurgency strategy, FM 3-24, promulgated by Petraeus in 2006, calls for securing the population from insurgents, and it suggests a troop density of 20 to 25 counterinsurgents for every 1,000 residents in an area of operation. If that formula was applied to parts of southern and eastern Afghanistan where the Taliban is strongest, at least tens of thousands of additional foreign troops would be needed.

By mid-April, Mullen and Gates had decided to replace McKiernan with McChrystal. Although McChrystal has a Special Forces counterterrorism background, he impressed Mullen and Gates with his thinking about counterinsurgency strategy in Afghanistan. Before he left for Kabul, Gates asked him to assess the mission and report back within 60 days.

To McChrystal and his senior advisers, the white paper was the strategy, and his job was to figure out how to implement it.

At the first meeting of a team of outside experts he convened to help him with the assessment, he told them, according to two attendees, that he wanted "a COIN campaign focused on the people."

After only a few weeks on the ground, it was evident to McChrystal that the situation was worse than he had expected and that there were far too few Afghan and NATO forces to protect the population. The hoped-for U.S. civilians were arriving too slowly. Although it was clear that asking for more troops would be controversial, it also seemed clear that the White House wanted a real counterinsurgency mission. And that would require more troops.

Back in Washington, some civilians involved in the review grew concerned that McChrystal's counterinsurgency plan went beyond what they believed was stated in the white paper. "Secure the population" was always a "military phrase," one senior civilian participant said. "That was the way they extrapolated from Riedel's plan," but "it's not in Riedel's plan."

To the military, however, the only way to do counterinsurgency is by protecting the population.

"We were operating under the assumption that when they said COIN, that's what they meant," said a senior U.S. military official in Afghanistan, "and they were serious about committing the necessary resources."

Last Tuesday evening, to prepare for a meeting the next day to discuss Afghanistan strategy with his national security team -- the first of several sessions to determine whether more troops will be sent -- Obama reread the white paper.